The present invention relates generally to a hermetic compressor assembly and, more particularly, to such a compressor having a plurality of compression chambers wherein the compression chambers empty into a common discharge chamber.
Hermetic compressors comprise a hermetically sealed housing having a compressor mechanism mounted therein. The compressor mechanism may include a crankcase or a cylinder block defining a plurality of compression chambers in which gaseous refrigerant is compressed and subsequently discharged into a common discharge cavity.
A disadvantage to prior compressor designs is that the valve performance of the discharge valves is reduced because of discharge pressure pulses (sometimes called cross talk) within the common discharge muffler cavity. During operation, each compression chamber injects a pulsed stream of compressed refrigerant into the discharge cavity. This discharge pulse of compressed refrigerant creates a pressure pulse that travels through the discharge cavity and impacts the discharge valves of the other compression chambers.
The impact of a pressure pulse against a discharge valve inhibits the opening of the valve during that valve's discharge cycle. By slowing the opening of the discharge valve, more energy is consumed in opening the valve and compressing the refrigerant, thereby creating a less efficient compressor.
The action of the pressure pulse retaining the discharge valve in the closed position increases the power consumption and reduces valve efficiency of the compressor. The increased power consumption also raises the temperature of the discharge valve. An increase in valve temperature may decrease the life span and effectiveness of the discharge valve leaf.
Some prior art compressors have tried to reduce the pressure pulses affecting each of the compression chambers by creating a bulkhead wall between the plurality of discharge valves and the outlet port of the common discharge chamber. A prior art compressor, such as U.S. Pat. No. 4,813,852, discloses a bulkhead wall dividing a common discharge chamber into sections which empty into a common outlet port. Each section contains a discharge valve assembly connected to an associated compression chamber. The pressure pulses from each discharge valve are separated from each other by means of the bulkhead wall isolating each discharge from each other. In this way, no discharge pulses or cross talk may affect other discharge valve assemblies.
A disadvantage of totally separating the discharge ports from one another is that the pressure within each section is increased with a possibility of reflecting the pressure pulse back into its originating discharge valve. The separated sections also increase the average back pressure on the valve, reducing the speed of the valve, thereby reducing compressor efficiency. The totally separated sections also reduce the ability of refrigerant to flow to the common discharge chamber outlet port.
The present invention is directed to overcoming the aforementioned problems associated with multi-cylinder compressors, wherein it is desired attenuate and reduce pressure pulses within a common discharge chamber while minimally restricting the refrigerant flow.